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    <script>
         /* 
      promise实例
        promise实例有两个属性
        - promiseState:代表的是当前promise实例的状态
          - pending:正在进行中(默认值,只有Promise构造函数的回调函数内部调用了resolve或reject才能改变)
          - fulfilled:成功状态
          - rejected:失败状态

        - promiseResult:promise实例的值(一般是Promise成功或者失败后需要携带的值)
          - 默认是undefined
          - 如果resolve或reject函数中传递了参数,则这个值就是他俩函数中的实参
    
    
    */
   const p1 = new Promise((resolve,reject)=>{
     setTimeout(()=>{
        console.log('异步操作完成');
        reject('err!!!')
     },2000)
   })
   console.log('p1',p1);
    </script>
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